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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of
the Securities Exchange Act of 1934 (Amendment No. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐

Preliminary Proxy Statement

☐

Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒

Definitive Proxy Statement

☐

Definitive Additional Materials

☐

Soliciting Material under §240.14a-12

MERSANA THERAPEUTICS, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

☒

No fee required.

☐

Fee paid previously with preliminary materials.

☐

Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

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MERSANA THERAPEUTICS, INC.
840 Memorial Drive
Cambridge, Massachusetts 02139

April 28, 2023

To Our Stockholders:

You are cordially invited to attend the 2023 Annual Meeting of Stockholders of Mersana Therapeutics, Inc., or the Annual Meeting, to be held at 10:00 a.m., Eastern time, on Thursday, June 8, 2023. The Annual Meeting will be a completely virtual meeting and will be conducted via live webcast. There will not be a physical location for the Annual Meeting, and you will not be able to attend the Annual Meeting in person. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/MRSN2023.

The Notice of Annual Meeting and Proxy Statement on the following pages describe the matters to be presented at the Annual Meeting. Details regarding how to attend the meeting and the business to be conducted at the Annual Meeting are more fully described in the Notice of Annual Meeting and Proxy Statement.

It is important that your shares be represented at the Annual Meeting. Whether or not you plan to attend the meeting online, we hope that you will have your stock represented by voting your shares over the internet, by telephone or, if you have requested to receive paper copies of these materials, by completing, signing, dating and returning the enclosed proxy card in the enclosed envelope, prior to the Annual Meeting. If you receive our Notice of Internet Availability of Proxy Materials, then instructions regarding how you can vote are contained in that notice. If you have requested to receive a proxy card, then instructions regarding how you can vote are contained on the proxy card. If your shares are held by a bank, broker or other agent, you will receive voting instructions from such bank, broker or other agent that you must follow for your shares to be voted. If you decide to attend the Annual Meeting, you will be able to vote your shares electronically, even if you have previously submitted your proxy.

Thank you for your continued support.

Sincerely,

/s/ Anna Protopapas

Anna Protopapas
Chief Executive Officer, President and Director

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[MISSING IMAGE: lg_mersanatherapeu-4c.jpg]

Mersana Therapeutics, Inc.
840 Memorial Drive
Cambridge, Massachusetts 02139

NOTICE OF 2023 ANNUAL MEETING OF STOCKHOLDERS
To Be Held on June 8, 2023

To Our Stockholders:

NOTICE IS HEREBY GIVEN that the 2023 Annual Meeting of Stockholders, or the Annual Meeting, of Mersana Therapeutics, Inc., a Delaware corporation, or Mersana or the Company, will be held on Thursday, June 8, 2023, at 10:00 a.m. ET. The Annual Meeting will be a completely virtual meeting and will be conducted via live webcast. Stockholders can attend the meeting via the internet at www.virtualshareholdermeeting.com/MRSN2023 and submit questions and vote shares electronically at the Annual Meeting.

The Annual Meeting is called for the following purposes:

To elect three Class III directors to serve until our 2026 annual meeting of stockholders and until their respective successors have been duly elected and qualified;

To approve, on a non-binding, advisory basis, the compensation of our named executive officers, as disclosed in our proxy statement;

To ratify the selection of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023;

To approve an amendment to our Fifth Amended and Restated Certificate of Incorporation, as amended, to eliminate the supermajority voting requirement applicable to changes to Article IV thereof;

To approve an amendment to our Fifth Amended and Restated Certificate of Incorporation, as amended, to reflect new Delaware law provisions regarding officer exculpation; and

To transact any other business that may properly come before the Annual Meeting or any adjournment or postponement thereof.

You can find more information regarding the foregoing in the attached proxy statement.

Each outstanding share of Mersana’s common stock (Nasdaq: MRSN) entitles the holder of record at the close of business on April 10, 2023, to receive notice of, and to vote at, the Annual Meeting or any adjournment or postponement of the Annual Meeting. A complete list of these stockholders will be available for examination by any stockholder during the ten days prior to the Annual Meeting for a purpose germane to the meeting at our offices at 840 Memorial Drive, Cambridge, Massachusetts 02139.

Instead of mailing a paper copy of our proxy materials to all of our stockholders, we are providing access to our proxy materials via the internet under the “notice and access” rules of the Securities and Exchange Commission. As a result, we are sending to our stockholders a Notice of Internet Availability of Proxy Materials, instead of a paper copy of this proxy statement and our annual report to stockholders for the fiscal year ended December 31, 2022, or the 2022 Annual Report. We plan to mail the Notice of Internet Availability of Proxy Materials on or about April 28, 2023, and the Notice of Internet Availability of Proxy Materials contains instructions on how to access our proxy materials over the internet and how each of our stockholders can receive a paper copy of the proxy materials, including the proxy statement, our 2022 Annual Report and a form of proxy card.

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Your vote is important. Whether or not you expect to attend the virtual Annual Meeting, please vote by telephone or through the internet or, if you receive a paper proxy card by mail, by completing, signing, dating and returning the proxy card mailed to you, as promptly as possible in order to ensure your representation at the Annual Meeting. Voting instructions are provided in the Notice of Internet Availability of Proxy Materials, or, if you receive a paper proxy card by mail, the instructions are printed on your proxy card and included in the accompanying Proxy Statement. Even if you have voted by proxy, if you attend the Annual Meeting, you may still vote online during the Annual Meeting. Please note, however, that if your shares are held of record by a bank, brokerage firm or other agent and you wish to vote online during the Annual Meeting, you must obtain a proxy issued in your name from that agent in order to vote your shares that are held in such agent’s name and account.

By Order of the Board of Directors

/s/ Alejandra Carvajal

Alejandra Carvajal
Secretary

Cambridge, Massachusetts
April 28, 2023

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	Page
Proxy Statement		1
Questions and Answers about These Proxy Materials and Voting		2
Proposal No. 1 — Election of Directors		9
Information Regarding the Board of Directors and Corporate Governance		13
Director Independence		13
Board Demographic Mix; Skills and Expertise		13
Board Meetings and Attendance		14
Board of Directors Leadership Structure		14
The Board of Directors’ Role in Risk Oversight		14
Code of Business Conduct and Ethics and Corporate Governance Guidelines		15
Board Committees		15
Audit Committee		16
Compensation Committee		18
Nominating and Corporate Governance Committee		19
Compensation Committee Interlocks and Insider Participation		20
Environmental, Social and Governance (“ESG”) Practices		21
Non-Employee Director Compensation		23
Executive Officers		27
Proposal No. 2 — Advisory Vote on Executive Compensation		28
Executive Compensation		29
Compensation Discussion and Analysis		29
Other Compensation Policies/Assessments		43
Report of the Compensation Committee of the Board of Directors		45
2022 Summary Compensation Table		46
Pay Ratio Disclosure		47
Pay Versus Performance		47
Grants of Plan-Based Awards		51
Outstanding Equity Awards at Fiscal Year-End Table		52
Option Exercises and Stock Vested		54
Employment Arrangements		54
Pension Benefits		54
Nonqualified Deferred Compensation		54
Payments on Termination of Employment or Change in Control Benefits		54
Potential Payments Upon Termination or Change of Control		56
Securities Authorized for Issuance Under Equity Compensation Plans		58
Security Ownership of Certain Beneficial Owners and Management		59

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	Page
Proposal No. 3 — Ratification of Selection of Independent Registered Public Accounting Firm for The Fiscal Year Ending December 31, 2023		62
Principal Accountant Fees and Services		62
Audit Committee Pre-Approval Policy and Procedures		62
Audit Committee Report		64
Certain Relationships and Related Party Transactions		65
Proposal No. 4 — Approval of Amendment To Fifth Amended and Restated Certificate of Incorporation, as Amended, to Eliminate the Supermajority Voting Requirement Applicable to Changes to Article IV Thereof		66
Proposal No. 5 — Approval of Amendment to Our Fifth Amended and Restated Certificate of Incorporation, As Amended, to Reflect New Delaware Law Provisions Regarding Officer Exculpation		69
General Matters		72
Appendix A		A-1
Appendix B		B-1

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Mersana Therapeutics, Inc.
840 Memorial Drive
Cambridge, Massachusetts 02139

Proxy Statement

For the 2023 Annual Meeting of Stockholders
To Be Held on Thursday, June 8, 2023 at 10:00 A.M. ET

This proxy statement, along with the accompanying Notice of 2023 Annual Meeting of Stockholders, is being furnished in connection with the solicitation of proxies by the board of directors of Mersana Therapeutics, Inc. for use at the 2023 Annual Meeting of Stockholders of Mersana Therapeutics, Inc., to be held at 10:00 a.m. ET via the internet at www.virtualshareholdermeeting.com/MRSN2023, including any postponement or adjournment thereof, which we refer to as the Annual Meeting.

In this proxy statement, we refer to Mersana Therapeutics, Inc. as “Mersana,” “the Company,” “we,” and “us.”

Important Notice Regarding the Availability of Proxy Materials
for the Annual Meeting of Stockholders to be Held on June 8, 2023:

This proxy statement and our 2022 Annual Report to Stockholders, or the 2022 Annual Report, are available for viewing, printing and downloading at www.proxyvote.com. To view these materials, please have your 16-digit control number(s) available that appears on your proxy card.

A copy of our Annual Report on Form 10-K for the fiscal year ended December 31, 2022, as filed with the Securities and Exchange Commission, or the SEC, except for exhibits, will be furnished without charge to any stockholder upon written request to: Mersana Therapeutics, Inc., 840 Memorial Drive, Cambridge, Massachusetts 02139, Attention: Secretary. Exhibits, if any, will be provided upon written request and payment of an appropriate processing fee. This Proxy Statement and our 2022 Annual Report are also available on the SEC’s website at http://www.sec.gov.

On or about April 28, 2023, we intend to mail a Notice of Internet Availability of Proxy Materials, or the Notice, to our stockholders (other than those who previously requested electronic or paper delivery of proxy materials), directing stockholders to a website where they can access our proxy materials, including this Proxy Statement and our 2022 Annual Report, and view instructions on how to vote online or by telephone. If you would prefer to receive a paper copy of our proxy materials, please follow the instructions included in the Notice. If you have previously elected to receive our proxy materials electronically, you will continue to receive access to those materials via e-mail unless you elect otherwise.

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Questions and Answers about These Proxy Materials and Voting

What is the purpose of this proxy statement?

We are sending you this proxy statement because the Board of Directors of Mersana is inviting you to vote (by soliciting your proxy) at our 2023 Annual Meeting of Stockholders to be held at 10:00 a.m. ET on Thursday, June 8, 2023, via a live webcast at www.virtualshareholdermeeting.com/MRSN2023, including any adjournments or postponements of the meeting, which we refer to as the Annual Meeting. This proxy statement along with the accompanying Notice of 2023 Annual Meeting of Stockholders summarizes the purposes of the Annual Meeting and information that is intended to assist you in making an informed vote on the proposals described in this proxy statement.

Why did I receive a one-page notice regarding the internet availability of proxy materials instead of a full set of proxy materials?

Pursuant to rules adopted by the SEC, we are providing access to our proxy materials over the internet, which reduces both the costs and the environmental impact of sending our proxy materials to stockholders. We intend to mail a Notice of Internet Availability of Proxy Materials to our stockholders (other than those who previously requested paper copies) on or about April 28, 2023.

The Notice contains instructions on how to:

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access and view the proxy materials over the internet;

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vote; and

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request a paper or e-mail copy of the proxy materials.

In addition, if you received paper copies of our proxy materials and wish to receive all future proxy materials, proxy cards, and annual reports electronically, please follow the electronic delivery instructions on www.proxyvote.com. We encourage stockholders to take advantage of the availability of the proxy materials on the internet to help reduce the cost and environmental impact of the Annual Meeting.

How do I attend the Annual Meeting?

Our Annual Meeting will be held in a virtual meeting format at www.virtualshareholdermeeting.com/MRSN2023. To participate in the Annual Meeting, you will need the 16-digit control number included in your Notice, your proxy card or on the instructions that accompanied your proxy materials. The meeting webcast will begin promptly at 10:00 a.m. ET. We encourage you to access the meeting prior to the start time. Online check-in will start 15 minutes before the meeting begins, and you should allow ample time for the check-in procedures. If your shares are held in a bank or brokerage account, instructions should also be provided on the voting instruction form provided by your bank or brokerage firm. Stockholders who wish to submit questions related to the business of the Annual Meeting may do so electronically starting at the time of check-in or during the meeting by clicking the option in the virtual meeting webcast portal. If you lose your 16-digit control number, you may join the Annual Meeting as a “Guest,” but you will not be able to vote or ask questions.

Who can vote at the Annual Meeting?

Only stockholders of record at the close of business on April 10, 2023, or the Record Date, will be entitled to vote at the Annual Meeting. On the Record Date, there were 109,069,315 shares of common stock outstanding and entitled to vote. A list of stockholders entitled to vote at the Annual Meeting will be available for examination at our offices at 840 Memorial Drive, Cambridge, Massachusetts 02139 during normal business hours by any stockholder for any purpose germane to the meeting for ten days prior to the Annual Meeting.

Stockholder of Record: Shares Registered in Your Name

If on the Record Date your shares were registered directly in your name with our transfer agent, Computershare Trust Company, N.A., then you are a stockholder of record. As a stockholder of record,

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you may vote online during the Annual Meeting or vote by proxy. Whether or not you plan to attend the Annual Meeting, we urge you to vote by proxy electronically through the internet, over the telephone or by completing and returning a printed proxy card that you may request or that we may elect to deliver at a later time to ensure your vote is counted.

Beneficial Owner: Shares Registered in the Name of a Bank or Broker

If on the Record Date your shares were held not in your name but rather in an account at a bank, brokerage firm or other similar organization, then you are the beneficial owner of shares held in “street name” and the Notice is being forwarded to you by that organization. The organization holding your account is considered to be the stockholder of record for purposes of voting at the Annual Meeting. As a beneficial owner, you have the right to direct your bank, broker or other agent regarding how to vote the shares in your account. You are also invited to attend the Annual Meeting. However, since you are not the stockholder of record, you may not vote your shares online during the Annual Meeting unless you request and obtain a valid proxy from your bank, broker or other agent.

On what matters am I voting?

There are five matters scheduled for a vote:

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Election of three Class III directors to serve until our 2026 annual meeting of stockholders and until their respective successors have been duly elected and qualified (Proposal 1);

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Approval, on a non-binding, advisory basis, of the compensation of our named executive officers, as disclosed in our proxy statement (commonly referred to as “Say-on-Pay”) (Proposal 2);

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Ratification of the selection of Ernst & Young LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2023 (Proposal 3);

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Approval of an amendment to our Fifth Amended and Restated Certificate of Incorporation, as amended, to eliminate the supermajority voting requirement applicable to changes to Article IV thereof, or the Capitalization Supermajority Elimination Amendment (Proposal 4); and

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Approval of an amendment to our Fifth Amended and Restated Certificate of Incorporation, as amended, to reflect new Delaware law provisions regarding officer exculpation, or the Officer Exculpation Amendment (Proposal 5).

What if another matter is properly brought before the Annual Meeting?

The Board of Directors knows of no other matters that will be presented for consideration at the Annual Meeting. If any other matters are properly brought before the meeting, it is the intention of the persons named in the accompanying proxy to vote on those matters in accordance with their best judgment.

How do I vote?

The procedures for voting are fairly simple:

Stockholder of Record: Shares Registered in Your Name

If you are a stockholder of record, you may vote by proxy through the internet, vote by proxy over the telephone, vote by proxy using a proxy card that you may request or that we may elect to deliver at a later time, or vote online during the Annual Meeting. Whether or not you plan to attend the Annual Meeting, we urge you to vote by proxy to ensure your vote is counted. You may still attend the Annual Meeting and vote online during the meeting even if you have already voted by proxy.

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By Internet. You may vote by proxy via the internet at www.proxyvote.com up until 11:59 p.m. ET on June 7, 2023, the day before the Annual Meeting by following the instructions provided on the Notice or the proxy card. You should have your proxy card in hand when you access the website and follow the instructions to obtain your records and to create an electronic voting instruction form.

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•

By Telephone. If you live in the United States or Canada, you may vote by proxy by calling toll-free 1-800-690-6903 and by following the instructions provided on the proxy card. You must have the 16-digit control number that is on either the Notice or the proxy card when voting.

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By Mail. If you received a proxy card, complete and mail your proxy card in the postage prepaid envelope you receive, and return the proxy card to Vote Processing, c/o Broadridge, 51 Mercedes Way, Edgewood, NY 11717. Your proxy will be voted in accordance with your instructions. If you sign and return the enclosed proxy but do not specify how you want your shares voted, they will be voted as recommended by our Board of Directors and according to the discretion of the proxy holders named in the proxy card upon any other business that may properly be brought before the meeting and at all adjournments and postponements thereof.

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By Attending the Virtual-only Annual Meeting. You may vote your shares at www.virtualshareholdermeeting.com/MRSN2023 during the Annual Meeting. You will need the 16-digit control number that is on either the Notice or the proxy card when voting and the instructions accompanying these proxy materials.

Beneficial Owner: Shares Registered in the Name of a Bank or Broker

If you are a beneficial owner of shares registered in the name of your bank, broker or other agent, you should have received a Notice containing voting instructions from that organization rather than from us. Simply follow the voting instructions in the Notice to ensure that your vote is counted. To vote online during the Annual Meeting, you must obtain a valid proxy from your bank, broker or other agent. Follow the instructions from your bank, broker or other agent included with these proxy materials, or contact that organization to request a proxy form.

We provide internet proxy voting to allow you to vote your shares online, with procedures designed to ensure the authenticity and correctness of your proxy vote instructions. However, please be aware that you must bear any costs associated with your internet access, such as usage charges from internet access providers and telephone companies.

How many votes do I have?

On each matter to be voted upon, you have one vote for each share of common stock you own as of the Record Date.

If I am a stockholder of record and I do not vote, or if I return a proxy card or otherwise vote without giving specific voting instructions, what happens?

If you are a stockholder of record and do not vote by completing a proxy card, by telephone, through the internet or online during the Annual Meeting, your shares will not be voted.

If you return a signed and dated proxy card or otherwise vote without marking voting selections, your shares will be voted, as applicable, “FOR” the election of each of the three nominees for director, “FOR” the approval of the compensation of our named executive officers, “FOR” the ratification of the selection of our independent registered public accounting firm, “FOR” the Capitalization Supermajority Elimination Amendment, and “FOR” the Officer Exculpation Amendment. If any other matter is properly presented at the Annual Meeting, your proxyholder (one of the individuals named on your proxy card) will vote your shares using his or her best judgment.

If I am a beneficial owner of shares held in street name and I do not provide my bank, broker or other agent with voting instructions, what happens?

If you are a beneficial owner of shares held in street name and you do not instruct your bank, broker or other agent how to vote your shares, your bank, broker or other agent may still be able to vote your shares in its discretion. In this regard, under the rules of the New York Stock Exchange, or NYSE, brokers that are subject to NYSE rules may vote your “uninstructed” shares with respect to certain matters, but not with respect to the election of directors, executive compensation matters and certain other matters. Of the matters to be voted on at the Annual Meeting, we expect the only proposal on which

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your broker will have discretionary authority is Proposal 3. These NYSE rules apply to voting your shares if you are the beneficial owner of shares held in street name notwithstanding that our common stock is traded on the Nasdaq Global Select Market, or Nasdaq.

When a beneficial owner of shares held in street name does not give voting instructions to his or her bank, broker or other securities intermediary holding his or her shares as to how to vote on a particular proposal in which such bank, broker or other agent does not have discretionary authority to vote on that proposal, such bank, broker, or other agent cannot vote the shares on that particular proposal. These un-voted shares are counted as “broker non-votes.”

If you a beneficial owner of shares held in street name, in order to ensure your shares are voted in the way you would prefer, you must provide voting instructions to your bank, broker or other agent by the deadline provided in the materials you receive from your bank, broker or other agent.

Who is paying for this proxy solicitation?

We will pay for the entire cost of soliciting proxies. We have retained Georgeson LLC to assist us in the solicitation of proxies for an aggregate fee of approximately $40,000. In addition to these proxy materials, our directors and employees may also solicit proxies in person, by telephone, or by other means of communication. Directors and employees will not be paid any additional compensation for soliciting proxies. We may also reimburse brokerage firms, banks and other agents for the cost of forwarding proxy materials to beneficial owners.

What does it mean if I receive more than one Notice?

If you receive more than one Notice, your shares may be registered in more than one name or in different accounts. Please follow the voting instructions on each of the Notices to ensure that all of your shares are voted.

Can I change my vote after submitting my proxy?

Stockholder of Record: Shares Registered in Your Name

Yes. You can revoke your proxy at any time before the final vote at the Annual Meeting. If you are the record holder of your shares, you may revoke your proxy in any one of the following ways:

•

You may submit another properly completed proxy card with a later date before the applicable deadline.

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You may grant a subsequent proxy by telephone or through the internet before the applicable deadline.

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You may send a timely written notice that you are revoking your proxy to our Corporate Secretary at 840 Memorial Drive, Cambridge, Massachusetts 02139.

•

You may attend the virtual Annual Meeting and vote online during the meeting.

Simply attending the Annual Meeting will not, by itself, revoke your proxy.

Your most current proxy card or telephone or internet proxy is the one that is counted.

Beneficial Owner: Shares Registered in the Name of Bank or Broker

If your shares are held by your bank, broker or other agent, you must follow the instructions provided by your bank, broker or other agent to revoke your proxy.

When are stockholder proposals and director nominations due for next year’s annual meeting?

Requirements for Stockholder Proposals to be Brought before an Annual Meeting

Our Second Amended and Restated Bylaws, or Bylaws, provide that, for stockholder director nominations or other proposals to be considered at an annual meeting of stockholders, the stockholder must give timely notice thereof in writing to our Secretary at c/o Mersana Therapeutics, Inc.,

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840 Memorial Drive, Cambridge, Massachusetts 02139. To be timely for the 2024 Annual Meeting of Stockholders, a stockholder’s notice must be delivered to or mailed and received by our Secretary at our principal executive offices between February 9, 2024 and March 10, 2024; provided that if the date of that annual meeting of stockholders is earlier than May 9, 2024, or later than August 7, 2024, you must give the required notice not earlier than the 120th day prior to the meeting date and not later than the 90th day prior to the meeting date or, if later than the 90th day prior to such meeting date, the 10th day following the day on which public disclosure of that meeting date is first made. A stockholder’s notice to the Secretary must also set forth the information required by our Bylaws.

Requirements for Stockholder Proposals to be Considered for Inclusion in Our Proxy Materials

Stockholder proposals submitted pursuant to Rule 14a-8 under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and intended to be presented at the 2024 annual meeting of stockholders must be received by us not later than December 30, 2023 in order to be considered for inclusion in our proxy materials for that meeting.

In addition to satisfying the advance notice provisions in our Bylaws relating to nominations of director candidates, to comply with the SEC’s universal proxy rule, shareholders who intend to solicit proxies in support of director nominees other than our nominees in compliance with Rule 14a-19 under the Exchange Act must provide notice that sets forth the information required by Rule 14a-19 under the Exchange Act no later than April 9, 2024. If the date of the 2024 annual meeting changes by more than 30 calendar days from the anniversary of the date of the Annual Meeting, such notice must instead be provided by the later of 60 calendar days prior to the date of the 2024 annual meeting or the 10th calendar day following our public announcement of the date of the 2024 annual meeting.

How many votes are needed to approve each proposal, and how are votes counted?

Proposal 1 — Election of Directors

As this is an uncontested election of directors, each nominee must receive a greater number of shares voted FOR his or her election than shares voted AGAINST his or her election to be elected. Shares held in street name by banks, brokers or other agents who indicate on their proxies that they do not have authority to vote the shares on Proposal 1 will not be counted as votes FOR or AGAINST Proposal 1 and will be treated as broker non-votes. Broker non-votes will have no effect on the voting on Proposal 1. If you vote to ABSTAIN on Proposal 1, your shares will not be voted FOR or AGAINST Proposal 1 and will not be counted as votes cast or shares voting on Proposal 1. As a result, voting to ABSTAIN will have no effect on the voting on Proposal 1.

Proposal 2 — Approval, on a non-binding, advisory basis, of the compensation of our named executive officers

To approval Proposal 2, the affirmative vote of a majority of the votes cast is required. Shares held in street name by a banks, brokers or other agents who indicate on their proxies that they do not have authority to vote the shares on Proposal 2 will not be counted as votes FOR or AGAINST Proposal 2 and will be treated as broker non-votes. Broker non-votes will have no effect on the voting on Proposal 2. If you vote to ABSTAIN on Proposal 2, your shares will not be voted FOR or AGAINST Proposal 2 and will not be counted as votes cast or shares voting on Proposal 2. As a result, voting to ABSTAIN will have no effect on the voting on Proposal 2.

Proposal 3 — Ratification of the selection of Ernst & Young LLP as our independent registered public accounting firm for the year ending December 31, 2023

The approve Proposal 3, the affirmative vote of a majority of the votes cast is required. If your shares are held by your bank, broker or other agent in street name and you do not timely provide voting instructions with respect to your shares, we expect that your bank, broker or other agent will have the authority to vote your shares on Proposal 3). If you vote to ABSTAIN on Proposal 3, your shares will not

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be voted FOR or AGAINST Proposal 3 and will not be counted as votes cast or shares voting on Proposal 3. As a result, voting to ABSTAIN will have no effect on the voting on Proposal 3.

Proposal 4 — Approval of an amendment to our Fifth Amended and Restated Certificate of Incorporation, as amended, to eliminate the supermajority voting requirement applicable to changes to Article IV thereof (the “Capitalization Supermajority Elimination Amendment”)

To approve Proposal 4, the affirmative vote of holders of at least seventy-five percent (75%) of the voting power of the shares of our common stock outstanding on the Record Date and entitled to vote at the Annual Meeting is required. Shares held in street name by banks, brokers or other agents who indicate on their proxies that they do not have authority to vote the shares on Proposal 4 will not be counted as votes FOR or AGAINST Proposal 4 and will be treated as broker non-votes. Broker non-votes will have the same effect as a vote AGAINST Proposal 4. If you vote to ABSTAIN on Proposal 4, your shares will not be voted FOR or AGAINST Proposal 4 and will not be counted as votes cast or shares voting on Proposal 4. Voting to ABSTAIN will have the same effect as a vote AGAINST Proposal 4.

Proposal 5 — Approval of an amendment to our Fifth Amended and Restated Certificate of Incorporation, as amended, to reflect new Delaware law provisions regarding officer exculpation (the “Officer Exculpation Amendment”)

To approve Proposal 5, the affirmative vote of holders of at least seventy-five percent (75%) of the voting power of the shares of our common stock outstanding on the Record Date and entitled to vote at the Annual Meeting is required. Shares held in street name by banks, brokers or other agents who indicate on their proxies that they do not have authority to vote the shares on Proposal 5 will not be counted as votes FOR or AGAINST Proposal 5 and will be treated as broker non-votes. Broker non-votes will have the same effect as a vote AGAINST Proposal 5. If you vote to ABSTAIN on Proposal 5, your shares will not be voted FOR or AGAINST Proposal 5 and will not be counted as votes cast or shares voting on Proposal 5. Voting to ABSTAIN will have the same effect as a vote AGAINST Proposal 5.

Votes will be counted by the inspector of election appointed for the Annual Meeting, who will separately count, for each proposal, votes “FOR” and “AGAINST,” abstentions and, if applicable, broker non-votes.

What is the quorum requirement?

A quorum of stockholders is necessary to hold a valid meeting. A quorum will be present if stockholders holding at least a majority in voting power of the outstanding shares entitled to vote are present at the Annual Meeting in person or represented by proxy. On the Record Date, there were 109,069,315 shares outstanding and entitled to vote. Thus, the holders of 54,534,658 shares must be present in person or represented by proxy at the Annual Meeting to have a quorum.

Your shares will be counted towards the quorum only if you submit a valid proxy (or one is submitted on your behalf by your bank, broker or other nominee) or if you vote online during the Annual Meeting. Abstentions and broker non-votes will be counted towards the quorum requirement. If there is no quorum, the chair of the meeting may adjourn the Annual Meeting to another date.

How can I find out the results of the voting at the Annual Meeting?

Preliminary voting results will be announced at the Annual Meeting. In addition, final voting results will be published in a current report on Form 8-K that we expect to file within four business days after the date of the Annual Meeting. If final voting results are not available to us in time to file a Form 8-K within four business days after the Annual Meeting, we intend to file a Form 8-K to publish preliminary results and, within four business days after the final results are known to us, file an amended Form 8-K to publish the final results.

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Who should I call if I have any additional questions?

If you hold your shares directly, please call Alejandra Carvajal, Secretary of the Company, at (617) 498-0020. If your shares are held in street name, please contact the telephone number provided on your voting instruction form or contact your broker or nominee holder directly.

Forward-Looking Statements

Statements in this proxy statement about future expectations, plans and prospects, as well as any other statements regarding matters that are not historical facts, may constitute “forward-looking statements” within the meaning of The Private Securities Litigation Reform Act of 1995. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “will,” “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including those discussed in the “Risk Factors” section of Mersana’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 28, 2023 and the risks described in other filings that Mersana may make with the Securities and Exchange Commission. Any forward-looking statements contained in this proxy statement speak only as of the date hereof, and Mersana specifically disclaims any obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise.

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Proposal No. 1 — Election of Directors

Our Fifth Amended and Restated Certificate of Incorporation, as amended, or the Certificate of Incorporation, states that the Board of Directors shall consist of not fewer than three and not more than fifteen members, and the precise number of directors shall be fixed by a resolution of the Board of Directors. The size of our Board of Directors is currently fixed at eight directors. Each director holds office until his or her successor is duly elected and qualified or until his or her earlier death, resignation or removal. Any vacancy in the Board of Directors, including a vacancy that results from an increase in the number of directors, may be filled by a vote of the majority of the directors then in office.

Our Certificate of Incorporation provides that the Board of Directors is divided into three classes, with the classes as nearly equal in number as possible. Each of our directors identified below serves in the class indicated. Subject to any earlier death, resignation or removal in accordance with the terms of our Certificate of Incorporation and Bylaws, our Class III directors, if elected at the Annual Meeting, will serve until the 2026 annual meeting of stockholders, our Class I directors will serve until the 2024 annual meeting of stockholders, and our Class II directors will serve until the 2025 annual meeting of stockholders. Any additional directorships resulting from an increase in the number of directors will be apportioned by the Board of Directors among the three classes.

Lawrence Alleva, David Mott and Anna Protopapas are the Class III directors whose terms expire at the Annual Meeting. Messrs. Alleva and Mott and Ms. Protopapas have each been nominated by the Board of Directors for and agreed to stand for election to the Board of Directors to serve as a Class III director for three years and until his or her successor is duly elected and qualified or until his or her earlier death, resignation or removal.

Our Bylaws provide for a majority voting standard for the election of directors in uncontested elections, which means that to be elected, a director nominee must receive a greater number of votes FOR his or her election than votes AGAINST from such election. The number of votes cast with respect to that director’s election excludes abstentions and broker non-votes with respect to that director’s election. In contested elections in which the number of director nominees exceeds the number of directors to be elected, the voting standard will be a plurality of the shares present online or by proxy and entitled to vote.

Our Nominating and Corporate Governance Committee is responsible for developing and recommending to our Board of Directors criteria for Board membership and, consistent with those criteria, recommending to the Board of Directors director candidates and nominees for the next annual meeting of stockholders. As reflected in our Corporate Governance Guidelines, it is the policy of the Board of Directors that all directors should possess the highest personal and professional ethics, integrity and values, and be committed to representing the long-term interests of our stockholders. The Nominating and Corporate Governance Committee seeks to assemble a Board of Directors that, as a whole, possesses the appropriate balance of professional and industry knowledge, financial acumen, and management experience necessary to oversee and direct Mersana’s business. The Nominating and Corporate Governance Committee and the Board of Directors also seek to attain diversity among directors of race, gender, geography, thought, viewpoints, and backgrounds. To those ends, the Nominating and Corporate Governance Committee has identified and evaluated nominees in the broader context of the overall composition of the Board of Directors, with the goal of recruiting members who complement and strengthen the skills of other members through diversity. The Nominating and Corporate Governance Committee will also consider whether to nominate any person proposed by a stockholder in accordance with the provisions of our Bylaws relating to stockholder nominations as described later in this proxy statement under the heading “General Matters — Stockholder Proposals and Nominations.”

The Board of Directors is currently comprised of eight members. Below is a list of the names, ages as of April 28, 2023 and classification of the individuals who currently serve as our directors.

Name	Age	Position
Willard H. Dere, M.D	69	Director (Class I)
Martin Huber, M.D.	63	Director (Class I)
Allene M. Diaz	58	Director (Class II)

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Name	Age	Position
Andrew A. F. Hack, M.D., Ph.D.	49	Director (Class II)
Kristen Hege, M.D.	59	Director (Class II)
Lawrence M. Alleva	73	Director (Class III)
David Mott	57	Chair of the Board of Directors (Class III)
Anna Protopapas	58	Director (Class III); Chief Executive Officer and President

Certain individual qualifications and skills of our directors that contribute to our Board of Directors’ effectiveness as a whole are described in the following paragraphs.

Nominees for Election as Class III Directors

Biographical information, including principal occupation, business experience and public company board experience during the last five years, for our nominees for election as Class III directors at the Annual Meeting is set forth below.

Lawrence M. Alleva has served as a member of our Board of Directors since September 2017. Prior to his retirement in June 2010, Mr. Alleva was employed by PricewaterhouseCoopers LLP, or PwC, a professional services firm, for 39 years, including 28 years as a partner. Mr. Alleva has served on the boards of directors of Bright Horizons Family Solutions Inc., an education and childcare company, since 2012; of Galera Therapeutics, Inc., an oncology radiation company, since June 2019; and of Adaptimmune Therapeutics plc, or Adaptimmune, a cell therapy company, since March 2015. He previously served as a director of TESARO, Inc., or TESARO, an oncology-focused company, from March 2012 until TESARO’s acquisition by GlaxoSmithKline plc, or GlaxoSmithKline, in January 2019. Mr. Alleva is a Certified Public Accountant (inactive). Mr. Alleva received a B.S. in accounting from Ithaca College and attended the Columbia University Executive MBA (non-degree) Program. We believe that Mr. Alleva’s extensive experience and expertise working with public companies on corporate finance and accounting matters as a Certified Public Accountant, his experience serving on other corporate boards and his experience in a senior leadership role at PwC provide him with the qualifications and skills to serve as a director.

David Mott has served as Chair of our Board of Directors since July 2012. Mr. Mott is a private investor through Mott Family Capital. From September 2008 until his retirement in February 2020, Mr. Mott served as a general partner of New Enterprise Associates, an investment firm focused on venture capital and growth equity investments, where he led the healthcare investing practice. Mr. Mott has served on the boards of directors of Adaptimmune since September 2014 and as chair thereof since January 2017; of Ardelyx, Inc., a biopharmaceutical company, since March 2009 and as chair thereof since March 2014; and of Novavax, Inc., a biotechnology company, since June 2020. He previously served as a director of Imara, Inc., a biotechnology company, from January 2016 and as chair of the board of directors from April 2016 until the reverse merger between Imara, Inc. and Enliven Therapeutics, Inc. in February 2023; of Epizyme, Inc., a biopharmaceutical company, from December 2009 and as chair of the board of directors from April 2016 until its acquisition by Ipsen Pharma SAS in August 2022; as a director of Nightstar Therapeutics plc, a gene therapy company, from August 2015 until its acquisition by Biogen Inc. in June 2019; and as a director of TESARO from May 2010 and as chair of the board of directors from July 2011 until its acquisition by GlaxoSmithKline in January 2019. Mr. Mott received a B.A. in economics and government from Dartmouth College. We believe that Mr. Mott’s leadership experience in the biotechnology industry, as well as his venture capital experience, especially his experience investing in life sciences companies, and his financial experience, provide him with the qualifications and skills to serve as director.

Anna Protopapas has served as our President and Chief Executive Officer and as a member of our Board of Directors since March 2015. Ms. Protopapas has served as chair of the board of directors of Nuvalent, Inc., or Nuvalent, a biotechnology company, since March 2022. She previously served as a director of Dicerna Pharmaceuticals, Inc., a biotechnology company, from January 2019 until June 2021. Ms. Protopapas received a B.S. in science and engineering from Princeton University, an M.S. in chemical engineering practice from the Massachusetts Institute of Technology and an M.B.A. from Stanford Graduate School of Business. We believe that Ms. Protopapas is qualified to serve as a member of our Board of

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Directors based on her experience in the pharmaceutical industry as well as her insight into our business as President and Chief Executive Officer of our company.

Recommendation of the Board of Directors

OUR BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT STOCKHOLDERS VOTE “FOR” EACH OF THE NOMINEES FOR CLASS III DIRECTORS.

Any properly submitted proxy will be voted in favor of the nominees unless a contrary specification is made in the proxy. The nominees have consented to serve as directors if elected. However, if any nominee is unable to serve or for good cause will not serve as a director, the persons named in the proxy intend to vote in their discretion for one or more substitutes who will be designated by our Board of Directors.

Directors Continuing in Office

Biographical information, including principal occupation, business experience and public company board experience during the last five years, for our current directors continuing in office is set forth below.

Class I Directors (Term Expires at 2024 Annual Meeting)

Willard H. Dere, M.D., has served as a member of our Board of Directors since March 2018. Dr. Dere has served as Professor Emeritus of Internal Medicine at the University of Utah and an advisor to Angitia Biopharmaceuticals, a biopharmaceutical company, since June 2022. In June 2022, Dr. Dere retired from the Utah Health Services Center, where he had served as Professor of Internal Medicine, B. Lue and Hope S. Bettilyon Presidential Endowed Chair in Internal Medicine for Diabetes Research, Co-Director of the Utah Clinical and Translational Science Institute and Co-Director of the Center for Genomic Medicine since June 2014 and as Associate Vice President for Research since July 2019. Dr. Dere has served on the boards of directors of BioMarin Pharmaceutical Inc., a biopharmaceutical company, since July 2016 and of Seres Therapeutics, Inc., a biotechnology company, since July 2017. He previously served as a director of Radius Health, Inc., a biopharmaceutical company, from November 2014 until its acquisition by Gurnet Point Capital, LLC and Patient Square Capital in August 2022. Dr. Dere received a B.A. and an M.D. from the University of California, Davis. We believe that Dr. Dere’s research, clinical and regulatory biopharmaceutical leadership experience qualify him to serve as a director.

Martin Huber, M.D., has served as a member of our Board of Directors since April 2020. Dr. Huber has served as President and Head of R&D of Xilio Therapeutics, Inc., or Xilio, a biotechnology company, since June 2022. He served as Xilio’s President of R&D from August 2021 to June 2022 and as Chief Medical Officer from April 2020 to June 2022. Prior to that, he served as Senior Vice President, Chief Medical Officer at TESARO from September 2015 to January 2019, and after TESARO’s acquisition by GlaxoSmithKline, he served as Senior Vice President, Clinical, from January 2019 to April 2020. Dr. Huber has served on the board of directors of Syndax Pharmaceuticals, Inc., a biotechnology company, since September 2021. Dr. Huber received a B.S. in biology from Texas Lutheran College and an M.D. from Baylor College of Medicine. We believe that Dr. Huber’s medical, clinical, and regulatory experience qualifies him to serve as a director.

Class II Directors (Term Expires at 2025 Annual Meeting)

Allene M. Diaz has served as a member of our Board of Directors since March 2021. Ms. Diaz has led AMD Consulting, a new product strategy and portfolio management consulting practice, since August 2020. She held the position of Senior Vice President of R&D Portfolio Management at GlaxoSmithKline from September 2019 to June 2020. From May 2015 to September 2019, she served as the Senior Vice President of Global Commercial Development and Program Strategy and as a member of the Executive Leadership Team at TESARO. Ms. Diaz has served on the board of directors of Ionis Pharmaceuticals, Inc., a biotechnology company, since June 2021. She previously served as a director of BCLS Acquisition Corp., a special purpose acquisition company, from October 2020 until November 2022, of Allena Pharmaceuticals, Inc., or Allena, a biopharmaceutical company, from April 2019 until September 2022, and of Erytech Pharma SA, a biopharmaceutical company, from September 2016 to September 2019. Ms. Diaz received a B.S. in psychology from Florida State University. We believe that Ms. Diaz’s experience in the commercial

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development and program strategy for oncology assets and her executive leadership and business experience in the biotechnology sector qualifies her to serve as a member of our Board of Directors.

Andrew A. F. Hack, M.D., Ph.D., has served as a member of our Board of Directors since January 2017. Dr. Hack has served as a Managing Director of Bain Capital Life Sciences, a private equity fund that invests in biopharmaceutical, specialty pharmaceutical, medical device, diagnostics, and life science technology companies globally, since March 2019. Before joining Bain Capital, Dr. Hack was the Chief Financial Officer of Editas Medicine, Inc., a biotechnology company, from July 2015 through March 2019. Dr. Hack has served on the boards of directors of Dynavax Technologies Corp., a biopharmaceutical company, since August 2019 and of Nuvalent since April 2021. He previously served as a director of BCLS Acquisition Corp. from October 2020 until November 2022; of Allena from June 2018 to June 2021; and of Atea Pharmaceuticals, Inc., a biopharmaceutical company, from May 2020 to June 2021. Dr. Hack received an A.B. in biology with special honors, an M.D. and a Ph.D. in molecular genetics and cell biology from the University of Chicago. We believe that Dr. Hack’s financial and medical background, as well as his experience in the biotechnology sector, qualify him to serve as a member of our Board of Directors.

Kristen Hege, M.D., has served as a member of our Board of Directors since August 2016. Dr. Hege recently retired as Senior Vice President, Early Clinical Development, Hematology/Oncology & Cell Therapy at Bristol Myers Squibb Company, or BMS, a global biopharmaceutical company, a position she held from November 2019, when BMS acquired Celgene Corporation, a pharmaceutical company, until March 2023. She joined Celgene Corporation in 2010 as Vice President, Translational Development. Dr. Hege has also held an active faculty position at the University of California, San Francisco Medical Center since 1996, most recently as Clinical Professor of Medicine, Hematology/Oncology, serving in that role as a volunteer since 2008. In February 2023, Dr. Hege was appointed to serve on the board of directors of Adaptimmune, effective as of November 1, 2023, and she has served on the board of directors of Graphite Bio, Inc., a biotechnology company, since April 2021. She also previously served as a director of Arcus Biosciences, Inc., a biopharmaceutical company, from October 2018 to November 2019. Dr. Hege received a B.A. in biochemistry summa cum laude from Dartmouth College and an M.D. from University of California, San Francisco. We believe that Dr. Hege’s medical background and experience in the biotechnology industry qualify her to serve as a director.

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Information Regarding the Board of Directors and Corporate Governance

Director Independence

Under Nasdaq Rule 5605, a majority of a listed company’s board of directors must generally be comprised of independent directors. In addition, Nasdaq rules require that, subject to specified exceptions and phase-in provisions, each member of a listed company’s audit committee, compensation committee and nominating and corporate governance committee be independent and, in the case of the audit committee and compensation committee, satisfy additional independence criteria set forth in Rules 10A-3 and 10C-1, respectively, under the Securities Exchange Act of 1934, as amended, or the Exchange Act.

Based upon information requested from and provided by each director concerning his or her background, employment and affiliations, including family relationships, in March 2023, the Board of Directors determined that each director, other than Ms. Protopapas, representing seven of our eight directors, or 87.5%, is “independent” as that term is defined under Nasdaq Rule 5605(a)(2). The Board of Directors also determined that each of the current members of our Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee satisfies the independence standards for such committee established by Rules 10A-3 and 10C-1 under the Exchange Act and the Nasdaq rules, as applicable. In making such determination, the Board of Directors considered the relationships that each such non-employee director has with Mersana and all other facts and circumstances deemed relevant in determining their independence.

There are no family relationships among any of our directors or executive officers.

Board Demographic Mix; Skills and Expertise

Our eight directors have provided the following responses on their self-identification of gender identity, demographic background, and self-identification as LGBTQ+:

Board Diversity Matrix (as of April 28, 2023)

Total Number of Directors

Female

Male

Part I: Gender Identity

Directors

Part II: Demographic Background

African American or Black

Alaskan Native or Native American

Asian

Hispanic or Latinx

Native Hawaiian or Pacific Islander

White

Two or More Races or Ethnicities

LGBTQ+

Did not Disclose Demographic Background

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In addition, our Board of Directors assessed the skills that each member contributes to address the specific needs of the Company, as reflected below:

Board Meetings and Attendance

The Board of Directors held five meetings during the year ended December 31, 2022. Each of the directors attended at least seventy-five percent (75%) of the meetings of the Board of Directors and the committees of the Board of Directors on which he or she served during the year ended December 31, 2022 (in each case, which were held during the period for which he or she was a director and/or a member of the applicable committee).

The non-employee directors regularly meet in executive session during regularly scheduled Board of Directors meetings, and the non-employee directors who serve on each of our standing committees regularly meet in executive session without management present during regularly scheduled meetings of such committees.

It is a policy of the Board of Directors that its members make every effort to attend our annual stockholder meetings. All of our directors attended the 2022 annual meeting of stockholders.

Board of Directors Leadership Structure

Our current Board leadership structure separates the positions of Chief Executive Officer and Chair of the Board of Directors, although we do not have a corporate policy requiring that structure. The Board of Directors believes that this separation is appropriate for Mersana at this time because it allows for a division of responsibilities and the sharing of ideas between individuals having different perspectives. Our Chief Executive Officer, who is also a member of our Board of Directors, is primarily responsible for our operations and strategic direction, while our Board Chair, who is an independent member of the Board of Directors, is primarily focused on matters pertaining to corporate governance, including management oversight and strategic guidance. The Board of Directors believes that this is the most appropriate structure at this time but, consistent with our Corporate Governance Guidelines, will make future determinations regarding whether or not to separate the roles of Chair and Chief Executive Officer based on then-current circumstances.

The Board of Directors’ Role in Risk Oversight

The Board of Directors plays an important role in risk oversight at Mersana through direct decision-making authority with respect to significant matters, as well as through the oversight of management by the Board of Directors and its committees. In particular, the Board of Directors administers its risk oversight function through (1) the review and discussion of regular periodic reports by the Board of Directors and its

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committees on topics relating to the risks that Mersana faces, (2) the required approval by the Board of Directors (or a committee of the Board of Directors to which the Board of Directors has delegated such responsibility) of significant transactions and other decisions, (3) the direct oversight of specific areas of our business by the Audit, Compensation and Nominating and Corporate Governance Committees and (4) regular periodic reports from the auditors and other outside consultants, including our compensation consultant, regarding various areas of potential risk, including, among others, those relating to our internal control over financial reporting and our compensation policies and practices. The Board of Directors also relies on management to bring significant matters impacting Mersana to its attention. Members of our senior management team attend meetings of our Board of Directors and its committees and are available to address any questions or concerns raised by our directors related to risk management and any other matters.

Pursuant to the Audit Committee’s charter, the Audit Committee is responsible for reviewing and discussing with management and our independent registered public accounting firm our system of internal controls, its financial and critical accounting practices and its policies relating to risk assessment and management. As part of this process, the Audit Committee discusses our major financial risk exposures and steps that management has taken to monitor and control such exposures. In addition, the Audit Committee has established procedures for the receipt, retention and treatment of complaints we may receive regarding accounting, internal accounting controls or auditing matters, and the confidential, anonymous submissions by employees of concerns regarding questionable accounting or accounting matters. The Audit Committee also oversees cybersecurity matters, including with respect to the integrity of our information technology systems, processes and data, and the Audit Committee periodically reviews and assesses with management the adequacy of controls and security thereof, along with contingency plans in the event of a breakdown or security breach affecting our information technology systems. Furthermore, the Audit Committee meets privately with representatives from our independent registered public accounting firm as part of its oversight of our risk management.

Pursuant to the Compensation Committee’s charter, the Compensation Committee oversees risk management activities relating to our compensation policies and practices and to succession planning for the members of our senior management. Pursuant to the Nominating and Corporate Governance Committee’s charter, the Nominating and Corporate Governance Committee oversees risk management activities relating to the composition of our Board of Directors and succession planning for our Board of Directors.

The Board of Directors believes that any leadership structure that it adopts must allow it to effectively oversee the management of the risks relating to Mersana’s operations. The Board of Directors acknowledges that there are different leadership structures that could allow it to effectively oversee the management of the risks relating to Mersana’s operations and believes its current leadership structure enables it to effectively provide oversight with respect to such risks.

Code of Business Conduct and Ethics and Corporate Governance Guidelines

We have adopted a Code of Business Conduct and Ethics that applies to all of our employees, officers and directors, including those officers responsible for financial reporting. A copy of our Code of Business Conduct and Ethics may be accessed free of charge by visiting our website at www.mersana.com and going to the “Corporate Governance” tab under the “Investors & Media” section, or by requesting a copy in writing from our Secretary at our Cambridge, Massachusetts office. We intend to post on our website any amendment to, or waiver under, a provision of the Code of Business Conduct and Ethics that applies to our directors and certain of our executive officers within four business days following the date of such amendment or waiver.

A copy of the Corporate Governance Guidelines may also be accessed free of charge by visiting our website at www.mersana.com and going to the “Corporate Governance” tab under the “Investors & Media” section, or by requesting a copy in writing from our Secretary at our Cambridge, Massachusetts office.

Board Committees

The Board of Directors has standing Audit, Compensation and Nominating and Corporate Governance Committees, each of which is comprised solely of independent directors and is described more fully below. Each committee operates pursuant to a written charter, and each reviews and assesses the adequacy of its

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charter periodically and submits its charter to the Board of Directors for approval. The charter for each committee is available on our website (www.mersana.com) under the “Corporate Governance” tab under the “Investors & Media” section. Additionally, each standing committee periodically performs, or participates in, under the oversight of the Nominating and Corporate Governance Committee, an evaluation of such committee against the requirements of the committee’s charter, the results of which are presented to the Board of Directors.

The following table describes which directors serve on each of the Board of Directors’ committees.

Name

Audit
Committee

Compensation
Committee

Nominating
and Corporate
Governance
Committee

Lawrence M. Alleva

X(1)

Willard H. Dere, M.D.

X(1)

Allene M. Diaz

Andrew A.F. Hack, M.D., Ph.D.

Kristen Hege, M.D.(2)

Martin H. Huber, M.D.

X(3)

David Mott

SEC Form DEF 14A filed by Mersana Therapeutics Inc.